Superjunction semiconductor device and method of manufacturing the same

ABSTRACT

A superjunction semiconductor device includes a first semiconductor layer doped with a first conductivity type; an active region formed on the first semiconductor layer, the active region including a drift layer; and a termination region disposed to surround the active region, the termination region including a lower edge region disposed on a side surface of the drift layer and an upper edge region disposed on the lower edge region, wherein the upper edge region includes a lower charge balance region disposed on the lower edge region, the lower charge balance region having a second conductivity type different from the first conductivity type, and an upper charge balance region disposed on the lower charge balance region, the upper charge balance region having the first conductivity type.

RELATED APPLICATIONS

This Application is a Continuation of U.S. application Ser. No.15/242,018, filed Aug. 19, 2016, which claims priority to and thebenefit of Korean Application No. 10-2015-0117345, filed Aug. 20, 2015,both of which are hereby incorporated by reference herein in theirentireties.

TECHNICAL FIELD

The present disclosure relates to a superjunction semiconductor deviceand a method of manufacturing the same, and more particularly, to asuperjunction semiconductor device including an alternating conductivitytype drift layer and a method of manufacturing the same.

BACKGROUND

Power MOSFET devices or insulated gate bipolar transistor (IGBT) devicesmay be used as switching devices in electronic devices. Such switchingdevices require a low on-resistance in an operating state, a highbreakdown voltage, and a high switching speed. Since the on-resistanceand the breakdown voltage generally have a trade-off relationship, it isdifficult to implement a switching device simultaneously satisfying alow on-resistance and a high breakdown voltage. Recently, it has beenreported that, among power MOSFET devices, a MOSFET device having asuperjunction structure including an alternating conductivity type driftlayer can simultaneously realize a low on-resistance and a highbreakdown voltage. However, as dopant concentrations of P-type andN-type regions in the alternating conductivity type drift layer aredecreased (or as breakdown voltages are increased), a field oxide isdamaged by a high voltage applied to a termination region surroundingthe P-type and N-type regions, and therefore, the reliability of theMOSFET device may be degraded.

SUMMARY

According to an aspect of the present disclosure, there is provided asuperjunction semiconductor device including: a first semiconductorlayer doped with a first conductivity type; an active region formed onthe first semiconductor layer, the active region including a driftlayer; and a termination region disposed to surround the active region,the termination region including a lower edge region disposed on a sidesurface of the drift layer and an upper edge region disposed on thelower edge region, wherein the upper edge region includes a lower chargebalance region disposed on the lower edge region, the lower chargebalance region having a second conductivity type different from thefirst conductivity type, and an upper charge balance region disposed onthe lower charge balance region, the upper charge balance region havingthe first conductivity type.

In exemplary embodiments, the upper charge balance region may bedisposed on substantially the entire area of the termination region.

In exemplary embodiments, the drift layer may include a first portionhaving the first conductivity type and a second portion having thesecond conductivity type, which extend along a first direction parallelto a top surface of the first semiconductor layer and are alternatelyarranged.

In exemplary embodiments, the lower edge region may include: first andsecond edge pillars respectively connected to the first and secondportions of the drift layer; and third and fourth edge pillars extendingin the first direction on one side of the drift layer, the third andfourth edge pillars not being respectively connected to the first andsecond portions of the drift layer. The first and third edge pillars mayhave the first conductivity type and the second and fourth edge pillarsmay have the second conductivity type.

In exemplary embodiments, the lower charge balance region may bedisposed on the first to fourth edge pillars.

In exemplary embodiments, the upper charge balance region may verticallyoverlap with the first to fourth edge pillars.

In exemplary embodiments, uppermost sidewalls of the first and secondportions of the drift layer may be in contact with a sidewall of theupper charge balance region.

In exemplary embodiments, an interface between the upper and lowercharge balance regions may be disposed to be spaced apart from a topsurface of the upper charge balance region in a third directionperpendicular to the top surface of the first semiconductor layer.

In exemplary embodiments, the lower charge balance region may have afirst impurity concentration, the second portion of the drift layer mayhave a second impurity concentration, and the first impurityconcentration may be smaller than the second impurity concentration.

In exemplary embodiments, the lower and upper charge balance regions mayform a P-N junction.

In exemplary embodiments, the drift layer may have a first height alonga third direction perpendicular to the top surface of the firstsemiconductor layer, the lower edge region may have a second heightalong the third direction, and the second height may be about 70% to 98%of the first height.

In exemplary embodiments, the drift layer may have a first height alonga third direction perpendicular to the top surface of the firstsemiconductor layer, the lower edge region may have a second heightalong the third direction, and the second height may be about 85% to 95%of the first height.

According to an aspect of the present disclosure, there is provided asuperjunction semiconductor device including an active region and atermination region surrounding the active region, wherein the activeregion includes: a first semiconductor layer having N-type conductivity;and a drift layer disposed on the first semiconductor layer, wherein thetermination region includes an upper edge region provided with a lowercharge balance region disposed on one side of the drift layer, the lowercharge balance region having P-type conductivity; and an upper chargebalance region disposed on the lower charge balance region, the uppercharge balance region having N-type conductivity.

In exemplary embodiments, the upper charge balance region may be formedon substantially the entire area of the termination region, and thelower charge balance region may vertically overlap with the upper chargebalance region.

In exemplary embodiments, the drift layer may include a plurality ofN-type pillars and a plurality of P-type pillars, which extend along afirst direction parallel to a top surface of the first semiconductorlayer and are alternately arranged.

In exemplary embodiments, the superjunction semiconductor device mayfurther include a lower edge region disposed under the upper chargebalance region, on a side surface of the drift layer. The lower edgeregion may include a plurality of first N-type edge pillars and aplurality of first P-type edge pillars, which are respectively connectedto the plurality of N-type pillars and the plurality of P-type pillars.

In exemplary embodiments, the lower edge region may include a pluralityof second N-type edge pillars and a plurality of second P-type edgepillars, which are disposed on one side of the plurality of first N-typeedge pillars and the plurality of first P-type edge pillars along asecond direction perpendicular to the first direction.

In exemplary embodiments, the lower charge balance region may bedisposed on the plurality of first N-type edge pillars, the plurality ofsecond N-type edge pillars, the plurality of first P-type edge pillars,and the plurality of second P-type edge pillars.

In exemplary embodiments, the lower charge balance region may include afirst region and a second region, which are located on the plurality offirst P-type edge pillars, and the first region may be located closer tothe drift layer than the second region. A third impurity concentrationof the first region may be substantially equal to a fourth impurityconcentration of the second region.

In exemplary embodiments, the lower charge balance region may include athird region and a fourth region, which are respectively located on twoof the plurality of second P-type edge pillars, and the third region maybe located closer to the drift layer than the fourth region. A fifthimpurity concentration of the third region may be substantially equal toa sixth impurity concentration of the fourth region.

In exemplary embodiments, the lower charge balance region may include afirst region and a second region, which are located on the plurality offirst P-type edge pillars, and the first region may be located closer tothe drift layer than the second region. A third impurity concentrationof the first region may be greater than a fourth impurity concentrationof the second region.

In exemplary embodiments, the lower charge balance region may include athird region and a fourth region, which are respectively located on twoof the plurality of second P-type edge pillars, and the third region maybe located closer to the drift layer than the fourth region. A fifthimpurity concentration of the third region may be greater than a sixthimpurity concentration of the fourth region.

In exemplary embodiments, the lower charge balance region may include afifth region and a sixth region, and the fifth region may be locatedcloser to the drift layer than the sixth region. The fifth region mayhave a first thickness along a third direction perpendicular to the topsurface of the first semiconductor layer, and the sixth region may havea second thickness smaller than the first thickness along the thirddirection.

According to an aspect of the present disclosure, there is provided amethod of manufacturing a superjunction semiconductor device, the methodincluding: forming a plurality of first active pillars and a pluralityof first edge pillars in a first semiconductor layer including an activeregion and a termination region; forming a second semiconductor layer onthe first semiconductor layer; forming a plurality of second activepillars and a plurality of preliminary charge balance layers in thesecond semiconductor layer; and annealing the first and secondsemiconductor layers such that the plurality of first active pillars andthe plurality of second active pillars are connected to each other bydiffusing impurities implanted into the plurality of first activepillars and the plurality of second active pillars.

In exemplary embodiments, forming the plurality of second active pillarsand the plurality of preliminary charge balance layers may includerespectively implanting impurities into the active region and thetermination region of the second semiconductor layer, using a second ionimplantation mask, thereby forming the plurality of second activepillars and the plurality of preliminary charge balance layers, and thesecond ion implantation mask may include a plurality of stripe-shapedfirst trenches extending in a first direction and a plurality ofopenings spaced apart from each other in the first direction and asecond direction perpendicular to the first direction.

In exemplary embodiments, forming the plurality of first active pillarsand the plurality of first edge pillars may include respectivelyimplanting impurities in the active region and the termination region ofthe first semiconductor layer, using a first ion implantation mask,thereby forming the plurality of first active pillars and the pluralityof first edge pillars, and the first ion implantation mask may include aplurality of stripe-shaped second trenches extending in a firstdirection and a plurality of stripe-shaped third trenches extending inthe first direction.

In exemplary embodiments, in the annealing, impurities implanted intothe plurality of first edge pillars and the plurality of preliminarycharge balance layers may be diffused, and the plurality of first edgepillars and the plurality of preliminary charge balance layers may beconnected to each other.

In exemplary embodiments, in the annealing, impurities implanted intothe plurality of preliminary charge balance layers may be diffused, andadjacent ones of the plurality of preliminary charge balance layers maybe connected to each other, thereby forming a lower charge balanceregion.

According to the embodiments, the superjunction semiconductor deviceincludes a lower charge balance region in an upper edge region of atermination region, and an upper charge balance region on the lowercharge balance region. The lower charge balance region has a P-typeconductivity and the upper charge balance region has an N-typeconductivity. The lower and upper charge balance regions may form a P-Njunction which is disposed along a vertical direction, and an interfaceof the P-N junction may be formed to be spaced apart by a predetermineddepth from an upper surface of the termination region. Thus, in an offstate of the superjunction semiconductor device, it is possible toprevent the phenomenon that a stress caused by electric fields, which isinduced by a high breakdown voltage, is concentrated in the vicinity ofthe upper surface of the termination region. Accordingly, a field oxidelayer formed on the upper surface of the termination region may not beeasily damaged by the high electric fields, and the superjunctionsemiconductor device may have excellent reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a top view illustrating a schematic configuration of asuperjunction semiconductor device according to exemplary embodiments.

FIG. 1B is a perspective view illustrating a portion of thesuperjunction semiconductor device of FIG. 1A.

FIG. 1C is a sectional view taken along line 1C-1C′ of FIG. 1A.

FIG. 2 is a sectional view illustrating a superjunction semiconductordevice according to exemplary embodiments.

FIGS. 3A and 3B are top views illustrating a superjunction semiconductordevice according to exemplary embodiments.

FIGS. 4A, 4B, and 4C illustrate a simulation result obtained throughExperimental Example 1 of a superjunction semiconductor device accordingto exemplary embodiments.

FIG. 5A is a perspective view illustrating a schematic configuration ofa superjunction semiconductor device according to exemplary embodiments.

FIG. 5B is a sectional view taken along line 5B-5B′ of FIG. 5A.

FIGS. 6A and 6B illustrate a simulation result obtained throughExperimental Example 2 of a superjunction semiconductor device accordingto exemplary embodiments.

FIG. 7 is a graph illustrating a surface electric field profile of asuperjunction semiconductor device according to exemplary embodiments.

FIGS. 8A, 8B, 9, 10, 11, 12, 13, 14A, 14B, 15, 16, 17, and 18 are viewsillustrating a method of manufacturing a superjunction semiconductordevice according to exemplary embodiments.

FIGS. 19A, 19B, and 20 are plan and sectional views illustrating amethod of manufacturing a superjunction semiconductor device accordingto exemplary embodiments.

FIGS. 21A, 21B, 22, and 23 are views illustrating a method ofmanufacturing a superjunction semiconductor device according toexemplary embodiments.

DETAILED DESCRIPTION

Certain exemplary embodiments of the present disclosure will now bedescribed in greater detail with reference to the accompanying drawingsto assist in a comprehensive understanding of constitution and effectsof the present disclosure. However, the present disclosure is notlimited to the embodiments disclosed herein, but can be implemented in avariety of configurations with a variety of modifications. Accordingly,it is apparent that the exemplary embodiments of the present disclosureare provided to perfect the present disclosure, and to inform thoseskilled in the art of the scope of the present disclosure completely.For convenience of explanation, in the accompanying drawings, certainelements may be enlarged from actual size, and the respective elementsmay be illustrated on an exaggerated or reduced scale.

When an element is stated as being “on” or “in contact with” anotherelement, it may be understood that the element may be contacted with, orconnected to another element directly, or contacted or connected via yetanother element which may be present in between. On the contrary, when acertain element is stated as being “directly on” or “in direct contactwith” another element, it may be understood that presence of anyintervening element therebetween is foreclosed. Other expressions suchas “between” and “directly between” that explain a relationship betweenelements may be interpreted likewise.

The expression of “first,” “second” or the like may be used to explain avariety of elements, but should not be construed as limiting theelements. The above expressions may be used exclusively for the purposeof distinguishing one element from another. For example, withoutdeparting from the scope of the present disclosure, the first elementmay be referred to as the second element, or likewise, the secondelement may be referred to as the first element.

Unless otherwise explicitly stated, a singular expression encompasses aplural expression. The wording such as “comprise” or “have” used hereinis intended to designate presence of characteristic, number, step,operation, element, component or a combination thereof, and may beinterpreted as being open to addition of one or more othercharacteristics, numbers, steps, operations, elements, components orcombination thereof.

Unless otherwise defined, the terms and expressions used herein may beinterpreted in their meanings as generally known to those skilled in theart.

Embodiments of the present disclosure are mainly illustrated togetherwith one example of superjunction MOSFET devices. However, the presentdisclosure is not limited thereto. The present disclosure may be appliedto other types of power switching techniques including IGBT devices,schottky rectifiers, several types of bipolar switches, several types ofthyristors, and rectifiers. Also, it is illustrated that the embodimentsof the present disclosure exemplarily include n-channel MOSFETs.However, the present disclosure is not limited thereto, and may beapplied to devices having the opposite conductivity type.

Hereinafter, preferred embodiments of the present disclosure will bedescribed in detail with reference to the accompanying drawings.

FIG. 1A is a top view illustrating a schematic configuration of asuperjunction semiconductor device according to exemplary embodiments,FIG. 1B is a perspective view illustrating a portion of thesuperjunction semiconductor device 100 of FIG. 1A, and FIG. 1C is asectional view taken along line 1C-1C′ of FIG. 1A. In FIG. 1B, somecomponents including a field plate 188, a gate electrode 190, and thelike are omitted for convenience of description. These components are,however, illustrated in FIG. 1C.

Referring to FIGS. 1A to 1C, the superjunction semiconductor device 100may include an active region AR and a termination region TR surroundingthe active region AR. The termination region TR may be located on thesame level as the active region AR while surrounding a sidewall of theactive region AR.

The active region AR may include a first semiconductor layer 110 and adrift layer 120 disposed on the first semiconductor layer 110.

In exemplary embodiments, the first semiconductor layer 110 may be aportion of a semiconductor substrate doped with an N-type impurity at ahigh concentration. In some implementations, although not shown, thefirst semiconductor layer 110 may collectively refer to a semiconductorsubstrate doped with an N-type impurity at a high concentration, and anepitaxial layer formed on the semiconductor substrate where theepitaxial layer is doped with an N-type impurity at a highconcentration.

In exemplary embodiments, the drift layer 120 may have a superjunctionstructure in which a first portion 122 including an N-type impurity anda second portion 124 including a P-type impurity are alternatelydisposed along a first direction (e.g., an X direction of FIG. 1B)parallel to a top surface of the first semiconductor layer 110. Here,each of the first and second portions 122 and 124 has a predeterminedwidth in the first direction, and may have a stripe shape extending in asecond direction (e.g., a Y direction of FIG. 1B) perpendicular to thefirst direction. In FIG. 1C, it is exemplarily illustrated that twofirst portions 122 and two second portions 124 are alternately disposedin the active region AR. However, the widths and numbers of the firstand second portions 122 and 124 may be changed based on a function, asize, a use voltage, etc. of the superjunction semiconductor device 100.

In exemplary embodiments, the concentration of the N-type impurity ofthe first portion 122 may be equal to that of the P-type impurity of thesecond portion 124, and a first width of the first portion 122 along theX direction may be equal to a second width of the second portion 124along the X direction. In this case, the balance between N-type andP-type charges respectively included in the first and second portions122 and 124 inside the drift layer 120 can be maintained. In anotherembodiments, the concentration of the N-type impurity of the firstportion 122 may be higher than that of the P-type impurity of the secondportion 124, and the first width of the first portion 122 along the Xdirection may be smaller than the second width of the second portion 124along the X direction. In this case, the concentrations of the N-typeand P-type impurities and the first and second widths may beappropriately selected such that the balance between N-type and P-typecharges respectively included in the first and second portions 122 and124 inside the drift layer 120 can be maintained. In still anotherembodiments, the concentration of the N-type impurity of the firstportion 122 may be lower than that of the P-type impurity of the secondportion 124, and the first width of the first portion 122 along the Xdirection may be greater than the second width of the second portion 124along the X direction.

In exemplary embodiments, a P body region 170 adjacent to an uppersurface of the drift layer 120 may be disposed over the second portion124 of the drift layer 120, and a P+ region 172 may be disposed insidethe P body region 170. Two N+ regions 174 may be disposed in the P+region 172. Here, the two N+ regions 174 have a predetermined depth fromthe upper surface of the drift layer 120, and are spaced apart from eachother. A gate dielectric layer 176 may be disposed on the first portion122 of the drift layer 120, and an active poly gate layer 178 may bedisposed on the gate dielectric layer 176. A spacer 180 made of, forexample, silicon nitride may be conformally disposed over the activepoly gate layer 178, and an insulating layer 182 may be disposed overthe spacer 180. A source electrode 184 may be disposed over theinsulating layer 182. The source electrode 184 may be in contact with atop surface of the P+ region 172.

The termination region TR may be disposed to surround the drift layer120 above the first semiconductor layer 110. The termination region TRmay include a lower edge region 130 located on the substantially samelevel as a lower portion of the drift layer 120. The lower edge region130 may be disposed on a side surface 120S of the drift layer 120. Thetermination TR may also include an upper edge region 140 surrounding thedrift layer 120 and disposed on (e.g., disposed above) the lower edgeregion 130.

The lower edge region 130 may include N-type and P-type pillarsalternately disposed along the X direction of FIG. 1B on the firstsemiconductor layer 110. As the lower edge region 130 has asuperjunction structure in which the N-type and P-type pillars arealternately disposed, the breakdown voltage of the superjunctionsemiconductor device 100 may increase.

In exemplary embodiments, the lower edge region 130 may include first tofourth edge pillars 132, 134, 136, and 138. The first and second edgepillars 132 and 134 may be portions of the N-type and P-type pillars,respectively. The first and second edge pillars 132 and 134 may berespectively connected to the first and second portions 122 and 124 ofthe drift layer 120. The third and fourth edge pillars 136 and 138 maybe respectively N-type and P-type pillars not connected to the activeregion AR, the N-type and P-type pillars extending in the Y direction.

In exemplary embodiments, the width of the first edge pillar 132 alongthe X direction may be substantially equal to the first width of thefirst portion 122 of the drift layer 120, and the width of the secondedge pillar 134 along the X direction may be substantially equal to thesecond width of the second portion 124 of the drift layer 120. However,the present disclosure is not limited thereto. In addition, the widthsof the third and fourth edge pillars 136 and 138 along the X directionmay be respectively equal to or different from those of the first andsecond edge pillars 132 and 134 along the X direction. The widths of thethird and fourth edge pillars 136 and 138 along the X direction may beappropriately selected based on a function, a size, a use voltage, etc.of the superjunction semiconductor device 100.

The upper edge region 140 may include a lower charge balance region 150and an upper charge balance region 160.

In exemplary embodiments, the upper charge balance region 160 may bedisposed throughout substantially the entire area of the terminationregion TR as exemplarily shown in FIG. 1B. For example, the upper chargebalance region 160 may be disposed to vertically overlap with the firstto fourth edge pillars 132, 134, 136, and 138 of the lower edge region130. The upper charge balance region 160 may be an N-type regionincluding an N-type impurity.

In exemplary embodiments, the lower charge balance region 150 may bedisposed between the upper charge balance region 160 and the lower edgeregion 130. A bottom surface of the lower charge balance region 150 maybe in contact with top surfaces of the first to fourth edge pillars 132,134, 136, and 138 of the lower edge region 130. The lower charge balanceregion 150 may be a P-type region including a P-type impurity. The lowercharge balance region 150 may have various P-type impurity concentrationprofiles on an X-Y plane. For example, the lower charge balance region150 may have a constant P-type impurity concentration profiles on theX-Y plane. Alternatively, the lower charge balance region 150 may have aperiodic concentration profile having a periodic increase and decreasein impurity concentration along each of the X and Y directions. Theimpurity concentration profile of the lower charge balance region 150will be described in detail later with reference to FIGS. 4B and 6B.

In exemplary embodiments, an interface between the lower and uppercharge balance regions 150 and 160 may be disposed throughout thesubstantially entire area of the termination region TR to verticallyoverlap with the first to fourth edge pillars 132, 134, 136, and 138.For example, the interface between the lower and upper charge balanceregions 150 and 160 may be a flat surface (e.g., a substantially planarsurface, a surface aligned within a plane) continuously formed on theX-Y plane. The lower and upper charge balance regions 150 and 160 mayform a P-N junction structure disposed in the vertical direction.Accordingly, in an off state of the superjunction semiconductor device100, a high electric field applied to a junction surface of the P-Njunction structure (or the interface between the lower and upper chargebalance regions 150 and 160) can be located to be spaced by apredetermined depth in a Z direction from a top surface of the uppercharge balance region 160. Thus, an electric field applied to a surfaceof the upper charge balance region 160 can be decreased, and a stresscaused by the high electric field is prevented from being applied to afield oxide layer 186 disposed on the upper charge balance region 160,thereby increasing the breakdown voltage of the superjunctionsemiconductor device 100.

As shown in FIG. 1B, the drift layer 120 may have a first height H1along the Z direction, and the lower edge region 130 may have a secondheight H2 along the Z direction. The second height H2 of the lower edgeregion 130 may be smaller than the first height H1 of the drift layer120. For example, bottom surfaces of the drift layer 120 and the loweredge region 130 may be located on the same vertical (Z direction) level,and a top surface of the drift layer 120 may be located on a highervertical level than that of a top surface of the lower edge region 130.In exemplary embodiments, the second height H2 of the lower edge region130 may be greater than or equal to 70% of the first height H1 of thedrift layer 120 and may be smaller than or equal to 98% of the firstheight H1 of the drift layer 120. For example, the second height H2 ofthe lower edge region 130 may be greater than or equal to 85% of thefirst height H1 of the drift layer 120 and may be smaller than or equalto 95% of the first height H1 of the drift layer 120. However, thepresent disclosure is not limited thereto.

As the second height H2 of the lower edge region 130 decreases, theheights of the N-type and P-type pillars alternately disposed in thelower edge region 130 decreases, and accordingly, the breakdown voltageof the superjunction semiconductor device 100 may decrease. For example,according to a simulation result obtained by changing the second heightH2, a breakdown voltage of 720 V was obtained when the second height H2was about 92% of the first height H1, and a breakdown voltage of 672 Vwas obtained when the second height H2 was about 85% of the first heightH1. That is, it may be preferred that the heights of the N-type andP-type pillars be selected as large values so as to increase thebreakdown voltage of the superjunction semiconductor device 100.

On the other hand, when the second height H2 of the lower edge region130 is excessively large (e.g., when the difference between the secondheight H2 of the lower edge region 130 and the first height H1 of thedrift layer 120 is excessively small), the height of the upper edgeregion 140 may be relatively small, and accordingly, it may be difficultto stably form the P-N junction structure in the upper edge region 140in which the lower and upper charge balance regions 150 and 160 arevertically disposed. Particularly, it is difficult to sufficientlysecure a spacing distance along the Z direction between the top surfaceof the upper charge balance region 160 and the interface between thelower and upper charge balance regions 150 and 160, and therefore, ahigh electric field may be applied to the surface of the upper chargebalance region 160 in an off state of the superjunction semiconductordevice 100.

As exemplarily shown in FIG. 1B, the first and second edge pillars 132and 134 of the lower edge region 130 are respectively connected to thefirst and second portions 122 and 124 of the drift layer 120 locatedinside the active region AR, so that both the first edge pillar 132 andthe first portion 122 can constitute an N-type pillar and both thesecond edge pillar 134 and the second portion can constitute a P-typepillar. The N-type and P-type pillars may extend along the Y-directionof FIG. 1B. Therefore, the electric field applied to the active regionAR may reach an outer wall of the termination region TR (or a sidewallportion of the termination region TR, located most distant from theactive region AR) at a relatively high speed along the Y-direction,i.e., the extending directions of the N-type and P-type pillars.However, in the case of the transmission of an electric field along theX direction, as a plurality of N-type and P-type pillars are alternatelydisposed in the X direction and have a superjunction structure, theelectric field applied to the active region AR may reach the outer wallof the termination region TR at a relatively low speed along the Xdirection. That is, there may occur a phenomenon that electric fieldsare asymmetrically transmitted along the X and Y directions in the loweredge region 130. Here, the transmission of an electric field along theextending direction (i.e., the Y direction) of the N-type and P-typepillars may be faster.

On the other hand, in the upper edge region 140, the N-type and P-typepillars may not extend in the termination region TR. The first portion122 of the drift layer 120 located on the same level as the upper edgeregion 140 may be in contact with the vertically arranged lower andupper charge balance regions 150 and 160. Also, the second portion 124of the drift layer 120 located on the same level as the upper edgeregion 140 may be in contact with the vertically arranged lower andupper charge balance regions 150 and 160. The lower and upper chargebalance regions 150 and 160 constitute a P-N junction in the verticaldirection, the impurity concentration and/or a vertical thicknessvariation of the lower and upper charge balance regions 150 and 160along the X direction is substantially equal to those of the lower andupper charge balance regions 150 and 160 along the Y direction. Thus,the electric fields applied to the active region AR can be transmittedup to the outer wall of the termination region TR at the substantiallysame speed along the X and Y directions. Accordingly, it is possible toprevent a phenomenon that electric fields are asymmetrically transmittedalong the X and Y directions in the upper edge region 140.

In general, a semiconductor device having a superjunction structureincluding stripe-shaped N-type and P-type pillars has a structure inwhich the stripe-shaped N-type and P-type pillars extend even at theuppermost portion of a termination region. For example, when consideringa semiconductor device having a structure in which N-type and P-typepillars extending along the Y direction, the transmission speed of anelectric field along the extending direction of the N-type and P-typepillars, i.e., the Y direction, may be much higher than that of anelectric field along the X direction. This is because, while theelectric field can be easily transmitted by movement of an electron orhole carrier in one direction along the extending direction (Ydirection) of the N-type and P-type pillars, the electric field isgradually transmitted by depletion along the X direction as P-type andN-type regions are alternately disposed along a direction (X direction)perpendicular to the extending direction. Therefore, a portion of atermination region disposed along the extending direction (Y direction)of the N-type and P-type pillars may become a weak portion to which ahigh electric field is locally applied. On the other hand, a relativelylow electric field may be uniformly applied to a portion of thetermination region disposed along the direction (X direction)perpendicular to the extending direction. A field oxide layer, etc.,disposed on the weak portion is easily damaged or broken down by a highelectric field. Therefore, the overall breakdown voltage of thesemiconductor device decreases, or the semiconductor device is easilydamaged or broken down.

Unlike the semiconductor device, in the superjunction semiconductordevice 100 according to the exemplary embodiments, the N-type and P-typepillars are not formed in the upper edge region 140 disposed adjacent tothe field oxide layer 186, and thus it is possible to prevent thephenomenon that the electric field is asymmetrically transmitted by thepillars. Accordingly, a relatively low electric field can be uniformlyapplied throughout the entire area of the upper edge region 140.

In general, a semiconductor device having a superjunction structureincluding rounded quadrangular shaped P-type and N-type pillars asconnection region pillars in a connection region between a terminationregion and an active region has a structure in which the connectionregion pillars are disposed to surround the active region outside anouter circumferential portion of the active region. In this case, localcharge imbalance may easily occur at corner portions of the connectionregion pillars or portions between the connection region pillars andpillars in the active region. The portions at which the charge imbalanceoccurs may become weak portions that cause damage or breakdown of thesemiconductor device. Therefore, it is not easy to adjust the shape,width, disposition, impurity concentration, etc. of the connectionregion pillars so as to ensure charge balance between the connectionregion pillars or charge balance at portions at which the connectionregion pillars and the pillars in the active region are adjacent to eachother.

However, in the superjunction semiconductor device 100 according to theexemplary embodiments, the N-type and P-type pillars are not formed inthe upper edge region 140, and the lower charge balance region 150 canbe formed throughout substantially the entire area of the terminationarea TR. Particularly, in a process for forming the lower charge balanceregion 150, the lower charge balance region 150 can be formed throughoutsubstantially the entire area of the termination area TR through a heattreatment process for ion-implanting P-type impurities using an ionimplantation mask in which openings are regularly arranged in a matrixform and diffusing the P-type impurities. Thus, excellent charge balancecan be obtained even at a portion at which the active region AR and thelower charge balance region 150 are adjacent to each other. Further,accordingly, an electric field can be stably transmitted at an interfaceportion between the active region AR and the termination region TR.

As shown in FIG. 1C, the field oxide layer 186 may be disposed to apredetermined thickness on the upper charge balance region 160, and thefield plate 188 may be disposed on the field oxide layer 186. The gateelectrode 190 may be formed on the insulating layer 182 to be spacedapart from the source electrode 184. The gate electrode 190 may beelectrically connected to the field plate 188. A floating electrode 194may be disposed on the field oxide layer 186 to be spaced apart from thegate electrode 190. The floating electrode 194 may be located at an endof the termination region TR, thereby serving as a field-stop layer forstopping electric fields.

The above-described superjunction semiconductor device 100 may includethe upper charge balance region 160 formed on the entire area of thetermination region TR and the lower charge balance region 150 disposedunder the upper charge balance region 160. In the off state of thesuperjunction semiconductor device 100, an interface of the P-N junctionin the termination region TR may be formed to be spaced apart by apredetermined depth from the upper surface of the upper charge balanceregion 160, and the electric field applied to the surface of the uppercharge balance region 160 may decrease. Thus, the superjunctionsemiconductor device 100 can have a high breakdown voltage and excellentreliability.

FIG. 2 is a sectional view illustrating a superjunction semiconductordevice 100A according to exemplary embodiments. FIG. 2 is a sectionalview corresponding to the section taken along line 1C-1C′ of FIG. 1A. InFIG. 2, like reference numerals identical to those of FIGS. 1A to 1Cdesignate the same members, and therefore, their detailed descriptionswill be omitted herein.

Referring to FIG. 2, a transition region may be further formed betweenan active region AR and a termination region TR. The transition regionmay surround the active region AR, and the termination region TR maysurround the transition region. P-type and N-type pillars 124 A and 122Amay be alternately arranged along an X direction in the transitionregion. A plurality of P-type pillars 124A in the transition region maybe connected to each other through a diffusion region 192.

The width of the transition region may be determined by the width of thediffusion region 192. The width and impurity concentration of each ofthe N-type and P-type pillars 122A and 124A in the transition region maybe equal to those of each of first and second portions 122 and 124 ofthe active region AR. In this case, charge balance between the N-typeand P-type pillars 122A and 124A inside the transition region can bemaintained. In another embodiments, the N-type impurity concentration ofthe N-type pillar 122A in the transition region may be lower than theP-type impurity concentration of the P-type pillar 124A in thetransition region, and the width of the N-type pillar 122A along the Xdirection may be greater than that of the P-type pillar 124A along the Xdirection. In the case, the N-type and P-type impurity concentrationsand the widths may be appropriately selected such that the chargebalance between the N-type and P-type pillars 122A and 124A inside thetransition region can be maintained.

FIGS. 3A and 3B are top views illustrating a superjunction semiconductordevice 100B according to exemplary embodiments. FIG. 3A is a sectionalview corresponding to the section taken along line 3A-3A′ of FIG. 1B,and FIG. 3B is a sectional view corresponding to the section taken alongline 3B-3B′ of FIG. 1B. In FIGS. 3A and 3B, like reference numeralsidentical to those of FIGS. 1A to 1C designate the same members, andtherefore, their detailed descriptions will be omitted herein. Thesuperjunction semiconductor device 100B according to FIGS. 3A and 3B issimilar to the superjunction semiconductor device 100 described withreference to FIGS. 1A to 1C, particularly except that the P-typeimpurity concentration profile of a lower charge balance region 150 isdifferent. Therefore, the above-described difference will be mainlydescribed.

Referring to FIGS. 3A and 3B, a drift layer 120 may include first andsecond portions 122 and 124, and a lower edge region 130 may includefirst to fourth edge pillars 132, 134, 136, and 138. The first andsecond edge pillars 132 and 134 may be connected to the first and secondportions 122 and 124, respectively. The third and fourth edge pillars136 and 138 may extend in a Y direction outside an active region AR, andare not connected to the first and second portions 122 and 124.

The lower charge balance region 150 may be disposed to overlap with thefirst to fourth edge pillars 132, 134, 136, and 138 of the lower edgeregion 130 in a vertical direction (Z direction of FIG. 3B). The lowercharge balance region 150 is located on the same level as the first andsecond portions 122 and 124 of the drift layer 120, and may be disposedto surround the first and second portions 122 and 124.

In exemplary embodiments, the lower charge balance region 150 mayinclude a first region 152 and a second region 154, and the first andsecond regions 152 and 154 may be portions of the lower charge balanceregion 150 vertically overlapping with the second edge pillar 134 of thelower edge region 130. Here, a first distance D1 between the firstregion 152 and the active region AR may be smaller than a seconddistance D2 between the second region 154 and the active region AR. Forexample, the first region 152 may be disposed closer to a sidewall ofthe drift layer 120 than the second region 154.

In exemplary embodiments, the P-type impurity concentration of the firstregion 152 may be substantially equal to that of the second region 154.For example, a portion of the lower charge balance region 150, whichvertically overlaps with the second edge pillar 134, may have a constantP-type impurity concentration along a direction distant from the driftlayer 120. That is, the portion of the lower charge balance region 150,which vertically overlaps with the second edge pillar 134, may have aconstant or substantially equal P-type impurity concentration profilealong the Y direction of FIG. 3B.

In another embodiment, the portion of the lower charge balance region150, which vertically overlaps with the second edge pillar 134, may havea P-type impurity concentration profile having a periodicincrease/decrease along the direction distant from the drift layer 120.In this case, among sections segmented for each period in the P-typeimpurity concentration profile, a mean impurity concentration obtainedin a first section may be substantially equal to that obtained in asecond section. In exemplary embodiments, the lower charge balanceregion 150 may be formed by ion-implanting P-type impurities into anN-type epitaxial layer using an ion implantation mask including openingsregularly arranged in a matrix form and laterally diffusing theimplanted P-type impurities through a subsequent heat treatment process.In this case, the lower charge balance region 150 may have a P-typeimpurity concentration profile having a periodic increase/decrease.

In still another embodiment, the P-type impurity concentration of thefirst region 152 may be higher than that of the second region 154. Forexample, the portion of the lower charge balance region 150, whichvertically overlaps with the second edge pillar 134, may have a P-typeimpurity concentration gradually decreased along the direction distantfrom the drift layer 120. That is, the portion of the lower chargebalance region 150, which vertically overlaps with the second edgepillar 134, may have a P-type impurity concentration profile decreasedalong the Y direction of FIG. 3B. Therefore, the lower charge balanceregion 150 may include a first region 152 located close to the activeregion AR, the first region 152 being more P-rich, and a second region154 located distant from the active region AR, the second region 154being more N-rich. The first and second portions 122 and 124 of thedrift layer 120 extend in the Y direction, and the first region 152 maybe disposed close to the second portion 124 of the drift layer 120. Asthe P-rich first region 152 is disposed adjacent to the second portion124 of the drift layer 120, a rapid difference in carrier mobilitygenerated in the vicinity of a boundary between the active region AR anda termination region TR (e.g., a difference in P-type carrier mobilitybetween the second portion 124 and the first region 152) can bedecreased, and it is possible to prevent the phenomenon that electricfields are concentrated on the vicinity of the boundary. Thus, arelatively low electric field can be applied to the lower charge balanceregion 150. The effect that the electric field is decreased by theP-rich first region 152 will be described in detail later with referenceto FIG. 7.

In exemplary embodiments, the lower charge balance region 150 mayinclude a third region 156 and a fourth region 158. The third and fourthregions 156 and 158 may be respectively located on two fourth edgepillars 138 among a plurality of fourth edge pillars 138 of the loweredge region 130. Here, a third distance D3 between the third region 156and the active region AR may be smaller than a fourth distance D4between the fourth region 158 and the active region AR. For example, thethird region 156 may be disposed closer to a sidewall of the drift layer120 than the fourth region 158.

In exemplary embodiments, the P-type impurity concentration of the thirdregion 156 may be substantially equal to that of the fourth region 158.For example, a portion of the lower charge balance region 150, whichvertically overlaps with the fourth edge pillar 138, may have a constantP-type impurity concentration along the direction distant from the driftlayer 120. That is, the third and fourth regions 156 and 158respectively disposed on the two fourth edge pillars 138 may have thesame P-type impurity concentration.

In FIGS. 3A and 3B, it is exemplarily illustrated that, for convenienceof illustration, 12 second portions 124 are disposed in the activeregion AR, and two pairs of the fourth edge pillars 138 are disposed atboth sides of the active region AR, respectively. However, it can beunderstood that the number and width of second portions 124 and thewidth and number of fourth edge pillars 138 formed in the terminationregion TR may be changed based on a function, a size, and a use voltageof the superjunction semiconductor device 100B.

FIGS. 4A to 4C illustrate a simulation result obtained throughExperimental Example 1 of a superjunction semiconductor device accordingto exemplary embodiments.

FIG. 4A illustrates a sectional view of Experimental Example 1 in whichthe width, height, and number of each of third and fourth edge pillars136 and 138 are changed in the superjunction semiconductor device 100described with reference to FIGS. 1A to 1C. According to ExperimentalExample 1 illustrated in FIG. 4A, the second height H2 of the lower edgeregion 130 is about 92% of the first height H1 of the drift layer 120.

FIG. 4B illustrates a P-type impurity concentration profile of the lowercharge balance region 150 along line 4B-4B′ of FIG. 4A. Referring toFIG. 4B, the lower charge balance region 150 may have an impurityconcentration profile having a periodic increase/decrease along line4B-4B′. In the impurity concentration profile, the maximum concentrationwithin each period may correspond to the position of a portion of thelower charge balance region 150 under which a central portion of thefourth edge pillars 138 is disposed. However, the present disclosure isnot limited thereto.

As described above, the lower charge balance region 150 may be formed byion-implanting P-type impurities into an N-type epitaxial layer using anion implantation mask including openings regularly arranged in a matrixform and laterally diffusing the implanted P-type impurities through asubsequent heat treatment process. In this case, the lower chargebalance region 150 may have a P-type impurity concentration profilehaving a periodic increase/decrease. Here, the position of the openingmay correspond to the maxim concentration point in each period withinthe impurity concentration profile. Therefore, when the central portionof the fourth edge pillars 138 does not vertically overlap with theopening of the ion implantation mask, the maximum concentration point ineach period within the impurity concentration profile may not correspondto the position of the central portion of the fourth edge pillars 138.

Also, it can be seen that, in the impurity concentration profile, a meanimpurity concentration C(mean) is maintained as a substantially constantvalue throughout the entire length along line 4B-4B′ of the lower chargebalance region 150. Also, it can be seen that a third concentrationC3(156) of the third region 156 of the lower charge balance region 150has the substantially same value as a fourth concentration C4(158) ofthe fourth region 158 of the lower charge balance region 150. When theopenings of the ion implantation mask have the same width, the meanimpurity concentration C(mean) can be constantly maintained in theimpurity concentration profile.

FIG. 4C is a simulation result image illustrating an electric fielddistribution in an off state with respect to Experimental Example 1 ofFIG. 4A. Referring to FIG. 4C, it can be seen that a relatively lowelectric field is applied throughout the entire area of the terminationregion TR. Particularly, a relatively high electric field isconcentrated along a contact interface between the upper and lowercharge balance regions 160 and 150. However, according to ExperimentalExample 1, the contact interface between the upper and lower chargebalance regions 160 and 150 is disposed to be spaced apart by apredetermined depth from the top surface of the upper charge balanceregion 160, and the contact interface is not formed at the surface ofthe upper charge balance region 160. Thus, it can be seen that a lowelectric field is applied to the surface of the upper charge balanceregion 160.

FIG. 5A is a perspective view illustrating a schematic configuration ofa superjunction semiconductor device 100C according to exemplaryembodiments, and FIG. 5B is a sectional view taken along line 5B-5B′ ofFIG. 5A. In FIGS. 5A and 5B, like reference numerals identical to thoseof FIGS. 1A to 3B designate the same members, and therefore, theirdetailed descriptions will be omitted herein.

Referring to FIGS. 5A and 5B, an upper edge region 140A may include alower charge balance region 150A and an upper charge balance region160A. The lower charge balance region 150A may include a first region152A and a second region 154A, where the distance between the secondregion 154A and an active region AR may be greater than that between thefirst region 152A and the active region AR. The first region 152A andthe second region 154A may have a first thickness T1 and a secondthickness T2 along the vertical direction, respectively. The secondthickness T2 may be smaller than the first thickness T1. As exemplarilyshown in FIG. 5A, the thickness of the lower charge balance region 150Amay gradually decrease as it becomes distant from the active region AR,but the present disclosure is not limited thereto. Also, as exemplarilyshown in FIG. 5A, a contact interface between the upper and lower chargebalance regions 160A and 150A may be inclined at a predetermined anglewith respect to an X-Y plane.

As described above, the lower charge balance region 150A may be formedby ion-implanting P-type impurities into an N-type epitaxial layer usingan ion implantation mask including openings regularly arranged in amatrix form and laterally diffusing the implanted P-type impuritiesthrough a subsequent heat treatment process. In this case, thickness ofthe lower charge balance region 150A may be changed depending on a widthor spacing distance of the openings. Particularly, when the width of theopenings decreases as it becomes distant from the active region ARand/or when the spacing distance of the openings increases as it becomesdistant from the active region AR, as exemplarily shown in FIGS. 5A and5B, the thickness of the lower charge balance region 150A may decreaseas it becomes distant from the active region. However, the presentdisclosure is not limited thereto.

FIGS. 6A and 6B illustrate a simulation result obtained throughExperimental Example 2 of a superjunction semiconductor device accordingto exemplary embodiments.

FIG. 6A illustrates a sectional view of Experimental Example 2 in whichthe width, height, and number of each of third and fourth edge pillars136 and 138 are changed in the superjunction semiconductor device 100Cdescribed with reference to FIGS. 5A and 5B. According to ExperimentalExample 2 illustrated in FIG. 6A, the second height H2 of the lower edgeregion 130 is about 92% of the first height H1 of the drift layer 120.

FIG. 6B illustrates a P-type impurity concentration profile of the lowercharge balance region 150A along line 6B-6B′ of FIG. 6A. Referring toFIG. 6B, the lower charge balance region 150A may have an impurityconcentration profile having a periodic increase/decrease along line6B-6B′. It can be seen that, in the impurity concentration profile, themean impurity concentration C(mean) gradually decreases as it becomesdistant from the active region AR. Also, it can be seen that a thirdconcentration C3(156A) of a third region 156A of the lower chargebalance region 150A has a greater value than a fourth concentrationC4(158A) of a fourth region 158A of the lower charge balance region150A.

FIG. 7 is a graph illustrating a surface electric field profile of asuperjunction semiconductor device according to exemplary embodiments.

FIG. 7 illustrates surface electric field profiles through a simulationin an off state with respect to Experimental Example 2 described withreference to FIGS. 6A and 6B and Comparative Example. ComparativeExample 710 uses a structure in which a plurality of N-type and P-typepillars are alternately disposed in a termination region, and aplurality of poly field plates are disposed on a field oxide layer so asto prevent an electric field from being suddenly changed in thetermination region.

Referring to FIG. 7, it can be seen that while a suddenly high electricfield is periodically applied in Comparative Example 710, a relativelylow electric field is gradually applied throughout the entire surface inEmbodiment 720.

As described above, in Embodiment 720, the lower and upper chargebalance regions can form a P-N junction structure disposed in thevertical direction, a high electric field applied to a junction surfaceof the P-N junction structure (or the interface between the lower andupper charge balance regions) is located to be spaced apart from the topsurface of the upper charge balance region. Hence, it can be understoodthat the electric field applied to the surface of the upper chargebalance region decreases.

Also, as described above, the N-type and P-type pillars are alternatelydisposed in the termination region of Comparative Example 710 and extendin one direction, and the transmission of an electric field along theextending direction is considerably fast (i.e., a phenomenon thatelectric fields are asymmetrically transmitted). Hence, a portion of thetermination region, disposed along the extending direction, may become aweak portion to which a high electric field is locally applied. On theother hand, any P-type and N-type pillars are not formed on an uppersurface of Embodiment 720. Thus, it can be understood to prevent thephenomenon that electric fields are asymmetrically transmitted by thepillars, and a relatively low electric field can be uniformly appliedthroughout the entire surface of the upper charge balance region.

As described above, connection region pillars are disposed to surroundthe N-type and P-type pillars of the active region in the terminationregion of Comparative Example 710, and therefore, a weak portion may begenerated due to local charge imbalance. On the other hand, inEmbodiment 720, the lower charge balance region may be formed throughoutthe substantially entire area of the termination region through a heattreatment process for ion-implantation P-type impurities using an ionimplantation mask in which openings are regularly arranged and diffusingthe P-type impurities. Thus, it can be understood that excellent chargebalance can be obtained around the active region, and hence an electricfield can be stably transmitted at an interface portion between theactive region and the termination region.

FIGS. 8A to 18 are views illustrating a method of manufacturing thesuperjunction semiconductor device 100 according to exemplaryembodiments. Specifically, FIGS. 8A, 9 to 13, 14A, and 15 to 18 aresectional views corresponding to the section along line 1C-1C′ of FIG.1A, and FIGS. 8B and 14B are top views illustrating masks 210_1 and210_7 described in FIGS. 8A and 14A.

Referring to FIGS. 8A and 8B, a first epitaxial layer 120_1 may beformed on a first semiconductor layer 110 divided into an active regionand a termination region TR, and a first mask 210_1 may be disposed onthe first epitaxial layer 120_1.

In exemplary embodiments, the first semiconductor layer 110 may be aportion of a semiconductor substrate doped with an N-type impurity.Alternatively, the first semiconductor layer 110 may include asemiconductor substrate and an epitaxial layer formed on thesemiconductor substrate, the epitaxial layer being doped with an N-typeimpurity.

The first epitaxial layer 120_1 may be a semiconductor layer includingan N-type impurity. In a growth process of the first epitaxial layer120_1, the first epitaxial layer 120_1 may be doped with an N-typeimpurity such as arsenic (As) or phosphorus (P).

The first mask 210_1 may include a plurality of first active trenchesTR1A and a plurality of first edge trenches TR1B. The plurality of firstactive trenches TR1A may expose a top surface of the first epitaxiallayer 120_1 of the active region AR therethrough, and the plurality offirst edge trenches TR1B may expose a top surface of the first epitaxiallayer 120_1 of the termination region TR therethrough.

Referring to FIG. 9, a P-type impurity such as boron (B) may beimplanted in a predetermined dose into a portion of the first epitaxiallayer 120_1, which is not covered by the first mask 210_1 by performinga first ion implantation process S10. Accordingly, a plurality of firstpreliminary active pillar layers AP1 can be formed at upper portions ofthe first epitaxial layer 120_1 of the active region AR, exposed by theplurality of first active trenches TR1A, and a plurality of firstpreliminary edge pillar layers TP1 can be formed at upper portions ofthe first epitaxial layer 120_1 of the termination region TR, exposed bythe plurality of first edge trenches TR1B.

After that, the first mask 210_1 may be removed.

Referring to FIG. 10, a second epitaxial layer 120_2 may be formed onthe first epitaxial layer 120_1 in which the plurality of firstpreliminary active pillar layers AP1 and the plurality of firstpreliminary edge pillar layers TP1 are formed. The second epitaxiallayer 120_2 may be formed by performing the same process as the firstepitaxial layer 120_1. The second epitaxial layer 120_2 may be formed tohave the same thickness as the first epitaxial layer 120_1, but thepresent disclosure is not limited thereto.

Referring to FIG. 11, a second mask 210_2 may be disposed on the secondepitaxial layer 120_2. The second mask 210_2 may be similar to the firstmask 210_1 described with reference to FIG. 8A. The second mask 210_2may include a plurality of second active trenches TR2A and a pluralityof second edge trenches TR2B.

Referring to FIG. 12, a P-type impurity such as boron (B) may beimplanted in a predetermined dose into a portion of the second epitaxiallayer 120_2, which is not covered by the second mask 210_2, byperforming a second ion implantation process S20. Accordingly, aplurality of second preliminary active pillar layers AP2 can be formedat upper portions of the second epitaxial layer 120_2 of the activeregion AR, exposed by the plurality of second active trenches TR2A, anda plurality of second preliminary edge pillar layers TP2 may be formedat upper portions of the second epitaxial layer 120_2 of the terminationregion, exposed by the plurality of second edge trenches TR2B.

After that, the second mask 210_2 may be removed.

A structure shown in FIG. 13 can be obtained by repeating, severaltimes, the processes described with reference to FIGS. 10 to 12.

Referring to FIG. 13, first to sixth preliminary active pillar layersAP1, AP2, AP3, AP4, AP5, and AP6 and first to sixth preliminary edgepillar layers TP1, TP2, TP3, TP4, TP5, and TP6 may be formed in first tosixth epitaxial layers 120_1, 120_2, 120_3, 120_4, 120_5, and 120_6,respectively.

Referring to FIGS. 14A and 14B, a seventh epitaxial layer 120_7 may beformed on the sixth epitaxial layer 120_6. A seventh mask 210_7 may bedisposed on the seventh epitaxial layer 120_7.

The seventh mask 210_7 may include a plurality of seventh activetrenches TR7A and a plurality of edge openings TR7B.

The plurality of seventh active trenches TR7A may be similar to thefirst active trench TR1A of the first mask 210_1. The plurality ofseventh active trenches TR7A may have a line shape extending in onedirection.

In exemplary embodiments, the plurality of edge openings TR7B may be aplurality of holes regularly arranged in a matrix form. In FIG. 14A, itis exemplarily illustrated that the plurality of edge openings TR7B havea circular section along the horizontal direction, but the presentdisclosure is not limited thereto. The plurality of edge openings TR7Bmay have various horizontal sectional shapes such as an ellipticalshape, a quadrangular shape, a rectangular shape, a square shape, arhombic shape, a triangular shape, a pentagonal shape, a hexagonalshape, an octagonal shape, etc.

In exemplary embodiments, the size of each of the plurality of edgeopenings TR7B may be determined based on a width of the plurality ofseventh active trenches TR7A. For example, when the plurality of edgeopenings TR7B have a circular section, one edge opening TR7B is disposedin a second unit cell UC2, and a first radius R₁ of the edge openingTR7B may be determined such that an area UC1A of the seventh activetrench TR7A disposed in a first unit cell UC1 is the same as an areaUC2B of the edge opening TR7B disposed in the second unit cell UC2.Specifically, when the length of one side of the unit cell UC1 isdefined as a cell pitch P_(cell), and the seventh active trench TR7A hasa trench width W_(TR), the first radius R₁ of the edge opening TR7B maysatisfy the following equation.π×R ₁ ² =P _(cell) ×W _(TR)

As described above, a weak portion may be generated in the vicinity of aboundary between the active region and the termination region due tocharge imbalance. However, in the present disclosure, when a pluralityof edge openings TR7B are disposed to have the same area as the seventhactive trench TR7A in the unit cells UC1 and UC2, charge balance can beeffectively obtained. When the plurality of edge openings TR7B have acircular section, the centers of the plurality of edge openings TR7B aredisposed at the center of the second unit cell UC2, so that the firstradius R1 of the edge opening TR7B, the cell pitch Pcell, and the likecan be easily calculated to obtain the charge balance.

Referring to FIG. 15, a P-type impurity such as boron (B) may beimplanted in a predetermined dose into a portion of the seventhepitaxial layer 120_7, which is not covered by the seventh mask 210_7,by performing a seventh ion implantation process S70. Accordingly, aplurality of seventh preliminary active pillar layers AP7 can be formedat upper portions of the seventh epitaxial layer 120_7 of the activeregion AR, exposed by the plurality of seventh active trenches TR7A, anda plurality of preliminary charge balance layers TP7 can be formed atupper portions of the seventh epitaxial layer 120_7 of the terminationregion TR, exposed by the plurality of edge openings TR7B.

In exemplary embodiments, the plurality of edge openings TR7B may havethe first radius R₁ greater than the cell pitch P_(cell). As exemplarilyshown in FIG. 15, the width of each of the plurality of preliminarycharge balance layers TP7 may be greater than the trench width W_(TR) ofthe plurality of seventh preliminary active pillar layers AP7.

After that, the seventh mask 210_7 may be removed.

Referring to FIG. 16, an eighth epitaxial layer 120_8 may be formed onthe seventh epitaxial layer 120_7. In exemplary embodiments, thethickness of the eighth epitaxial layer 120_8 may be formed smaller thanthat of the seventh epitaxial layer 120_7.

Referring to FIG. 17, an annealing process may be performed on astructure in which the eighth epitaxial layer 120_8 is formed, therebydiffusing impurities implanted into the first to seventh preliminaryactive pillar layers AP1, AP2, . . . , AP6, and AP7 (see FIG. 16), thefirst to sixth preliminary edge pillar layers TP1, TP2, . . . , TP5, andTP6 (see FIG. 16), and the preliminary charge balance layer TP7 (seeFIG. 16), which are formed in the structure.

In exemplary embodiments, portions of the first to eighth epitaxiallayers 120_1, 120_2, . . . , 120_7, and 120_8, located in the activeregion AR, may be referred to as a drift layer 120, and portions of thefirst to sixth epitaxial layers 120_1, 120_2, . . . , 120_5, and 120_6,located in the termination region TR, may be referred to as a lower edgeregion 130.

In exemplary embodiments, the impurities may be diffused by apredetermined distance in the horizontal direction and/or the verticaldirection through the annealing process, and accordingly, the first toseventh preliminary active pillar layers AP1, AP2, AP6, and AP7 areconnected to each other along the vertical direction, to form a secondportion 124 extending in one direction. A portion of the drift layer120, located between adjacent two second portions 124 may be referred toas a first portion 122.

In addition, the first to sixth preliminary edge pillar layers TP1, TP2,. . . , TP5, and TP6 are connected to each other along the verticaldirection through the annealing process, to form P-type edge pillars inthe lower edge region 130. A portion of the lower edge region 130,located between the P-type edge pillars, may be referred to as N-typeedge pillars.

The impurities implanted into the preliminary charge balance layer TP7are diffused in the horizontal direction and/or the vertical direction,and overlap with the impurities implanted into an adjacent preliminarycharge balance layer TP7, thereby forming a lower charge balance region150. A portion of the eighth epitaxial layer 120_8, disposed on thelower charge balance region 150, may be referred to as an upper chargebalance region 160. In exemplary embodiments, the lower charge balanceregion 150 may be formed through the substantially entire area of thetermination region TR, and the upper charge balance region 160 mayvertically overlap with the lower charge balance region 150 throughoutthe substantially entire area of the termination region TR.

As the impurities are diffused in the horizontal direction through theannealing process, the concentration of P-type impurities included inthe lower charge balance region 150 may be smaller that that of P-typeimpurities included in the first portion 122 of the active region AR. Inaddition, as the impurities are diffused in the horizontal directionthrough the annealing process, the lower change balance region 150 isformed. Therefore, the lower charge balance area 150 may have a P-typeimpurity concentration profile having a periodic increase/decrease.

In general, as the concentration of impurities in a termination regiondecreases, the breakdown voltage of a semiconductor device may increase.Accordingly, the concentration of impurities in the termination regionis smaller than that of impurities included in a P-type pillar of anactive region, which may be advantageous to improve the breakdownvoltage. In order to form impurity regions having different impurityconcentrations in the active region and the termination region, whichare located on the same level, it is generally required to perform ionimplantation processes twice using different ion implantation doses.However, in the present disclosure, the active region AR and thetermination region TR, which have different impurity concentrations, canbe simultaneously formed through only one-time ion implantation process,using the seventh mask 210_7 including the stripe-shaped trenches TR7Afor the active region AR and the circular openings TR7B for thetermination region TR. Accordingly, processes can be simplified, andmanufacturing cost can be reduced.

Referring to FIG. 18, additional ion implantation processes for forminga P body region 170, a P+ region 172, and an N+ region 174 may beperformed on the active region AR. An oxidation process for forming agate dielectric layer 176 and a field oxide layer 186, a deposition andpatterning process for forming an active poly gate layer 178 and a fieldplate 188, a deposition and patterning process for forming a spacer 180and an insulating layer 182, a deposition and patterning process forforming a source electrode 184, a gate electrode 190, and a floatingelectrode 194, and the like may be performed before or after the ionimplantation processes or between the ion implantation processes.

The above-described processes are performed, thereby completing thesuperjunction semiconductor device 100 shown in FIG. 18.

FIGS. 19A to 20 are plan and sectional views illustrating a method ofmanufacturing the superjunction semiconductor device 100 according toexemplary embodiments. The method is similar to a method ofmanufacturing the superjunction semiconductor device 100, described withreference to FIGS. 8A to 18, except the shape of a seventh mask 210_7A.

Referring to FIG. 19A, the seventh mask 210_7A may include a pluralityof seventh active trenches TR7C and a plurality of edge openings TR7D.

In exemplary embodiments, the plurality of edge openings TR7D may be aplurality of holes regularly arranged in a matrix form. The plurality ofedge openings TR7D may be formed to have a smaller radius than the edgeopenings TR7D formed in the seventh mask 210_7 described with referenceto FIG. 14A.

For example, a second radius R₂ of the edge opening TR7D may bedetermined such that an area UC1C of the seventh active trench TR7Cdisposed in a first unit cell UC1 is the same as an area UC2D of theedge opening TR7D disposed in the second unit cell UC2. Specifically,when the sum of a distance between the seventh active trenches TR7C anda trench width WTR of the seventh active trench TR7C is defined as acell pitch P_(cell), and the seventh active trench TR7C has the trenchwidth W_(TR), the second radius R₂ of the edge opening TR7D may satisfythe following equation.π×R ₂ ² =P _(cell)/2×W _(TR)/2

As described above, a weak portion may be generated in the vicinity of aboundary between the active region and the termination region due tocharge imbalance. However, in the present disclosure, when a pluralityof edge openings TR7D are disposed to have the same area as the seventhactive trench TR7C in the unit cells UC1 and UC2, charge balance can beeffectively obtained. When the plurality of edge openings TR7D have acircular section, the centers of the plurality of edge openings TR7D aredisposed at the center of the second unit cell UC2, so that the secondradius R₂ of the edge opening TR7D, the cell pitch P_(cell), and thelike can be easily calculated to obtain the charge balance.

Referring to FIG. 19B, a seventh ion implantation process S70A isperformed using the seventh mask 210_7, so that a plurality of seventhpreliminary active pillar layers AP7A are formed in the active region ARand a plurality of preliminary charge balance layers TP7A are formed inthe termination region TR.

Referring to FIG. 20, an annealing process may be performed on astructure in which the plurality of seventh preliminary active pillarlayers AP7A and the plurality of preliminary charge balance layers TP7Aare formed.

Impurities implanted into the preliminary charge balance layer TP7A arediffused in the horizontal direction and/or the vertical directionthrough the annealing process, and overlap with impurities implantedinto an adjacent preliminary charge balance layer TP7A, thereby forminga lower charge balance region 150B. In exemplary embodiments, the lowercharger balance region 150B may be formed throughout the substantiallyentire area of the termination region TR. A portion of the eighthepitaxial layer 120_8, disposed on the lower charge balance region 150B,may be referred to as an upper charge balance region 160B.

After that, the process described with reference to FIG. 18 isperformed, thereby completing the superjunction semiconductor device100.

FIGS. 21A to 23 are views illustrating a method of manufacturing asuperjunction semiconductor device 100D according to exemplaryembodiments. The method is similar to a method of manufacturing thesuperjunction semiconductor device 100, described with reference toFIGS. 8A to 18, except the shape of a seventh mask 210_7B.

Referring to FIG. 21A, the seventh mask 210_7B may include a pluralityof seventh active trenches TR7E and a plurality of edge openings TR7F.

In exemplary embodiments, the plurality of edge openings TR7F may have acircular section having a third radius R₃ that gradually becomes smallas it becomes distant from the plurality of seventh active trenchesTR7E.

Therefore, the seventh mask 210_7B may include a first edge mask regionR1, a second edge mask region R2, and a third edge mask region R3, whichare sequentially disposed along a direction in which its distancebecomes distant from the plurality of seventh active trenches TR7E. Thefirst edge mask region R1 may be a mask region for forming a P-richregion having a relatively high P-type impurity concentration, and thethird edge mask region R3 may be a mask region for forming an N-richregion having a relatively high N-type impurity concentration.

Referring to FIG. 21B, a seventh ion implantation process S70B isperformed using the seventh mask 210_7B, so that a plurality of seventhpreliminary active pillar layers AP7B can be formed in an active regionand a plurality of preliminary charge balance layers TP7B can be formedin a termination region. Meanwhile, a portion of the preliminary chargebalance layer TP7B, exposed by the first edge mask region R1, may becomea P-rich region having a relatively high P-type impurity concentration,and a portion of the preliminary charge balance layer TP7B, exposed bythe third edge mask region R3, may become an N-rich region having arelatively high N-type impurity concentration.

Referring to FIG. 22, an annealing process may be performed on astructure in which the plurality of seventh preliminary active pillarlayers AP7B and the plurality of preliminary charge balance layers TP7Bare formed.

Impurities implanted into the preliminary charge balance layer TP7B arediffused in the horizontal direction and/or the vertical directionthrough the annealing process, and overlap with impurities implantedinto an adjacent preliminary charge balance layer TP7B, thereby forminga lower charge balance region 150C. In exemplary embodiments, as theconcentration of P-type impurities included in the preliminary chargebalance layer TP7B gradually decreases as it becomes distant from theactive region AR, the lower charge balance region 150C may have athickness that gradually decreases as it becomes distant from the activeregion AR.

Referring to FIG. 23, the process described with reference to FIG. 18 isperformed, thereby completing the superjunction semiconductor device100D.

Although preferred embodiments of the present disclosure have been shownand described in detail, the present disclosure is not limited there,and it will be apparent to those skilled in the art that variousmodifications and changes can be made thereto within the technicalspirit and the scope of the present invention.

What is claimed is:
 1. A superjunction semiconductor device, comprising:a semiconductor layer doped with a first conductivity type; an activeregion formed on the semiconductor layer, the active region including adrift layer; and a termination region around the active region, thetermination region including: a lower edge region disposed on a sidesurface of the drift layer, and an upper edge region disposed on thelower edge region, the upper edge region including: a lower chargebalance region disposed on the lower edge region, the lower chargebalance region having a second conductivity type different from thefirst conductivity type, the lower charge balance region having athickness that decreases with distance away from the active region, andan upper charge balance region disposed on the lower charge balanceregion, the upper charge balance region having the first conductivitytype.
 2. The superjunction semiconductor device of claim 1, wherein theupper charge balance region is disposed on substantially an entire areaof the termination region.
 3. The superjunction semiconductor device ofclaim 1, wherein the drift layer includes a first portion having thefirst conductivity type and a second portion having the secondconductivity type, the first portion and the second portion of the driftlayer extend along a direction parallel to a top surface of thesemiconductor layer and are alternately arranged.
 4. The superjunctionsemiconductor device of claim 1, wherein the lower edge region includes:first and second edge pillars respectively connected to first and secondportions of the drift layer; and third and fourth edge pillars on oneside of the drift layer, the third and fourth edge pillars not beingrespectively connected to the first and second portions of the driftlayer, the first and third edge pillars have the first conductivity typeand the second and fourth edge pillars have the second conductivitytype.
 5. The superjunction semiconductor device of claim 1, wherein anuppermost sidewall of a portion of the drift layer is in contact with asidewall of the upper charge balance region.
 6. The superjunctionsemiconductor device of claim 1, wherein the lower and upper chargebalance regions form a P-N junction.
 7. The superjunction semiconductordevice of claim 1, further comprising: a transition region disposedbetween the active region and the termination region.
 8. Thesuperjunction semiconductor device of claim 1, further comprising: atransition region disposed between the active region and the terminationregion, the transition region at least partially surrounding the activeregion, the termination region at least partially surrounding thetransition region.
 9. The superjunction semiconductor device of claim 1,further comprising: a transition region including a plurality of pillarshaving the second conductivity type; and a diffusion region connectingthe plurality of pillars.
 10. A superjunction semiconductor device,comprising: an active region; and a termination region around the activeregion, the active region including: a semiconductor layer having afirst conductivity type, and a drift layer disposed on the semiconductorlayer; the termination region including an upper edge region, the upperedge region including: a lower charge balance region disposed on oneside of the drift layer, the lower charge balance region having secondconductivity type, the lower charge balance region having a taperedshape, and an upper charge balance region disposed on the lower chargebalance region, the upper charge balance region having the firstconductivity.
 11. The superjunction semiconductor device of claim 10,wherein the upper charge balance region is formed on substantially anentire area of the termination region, and the lower charge balanceregion vertically overlaps with the upper charge balance region.
 12. Thesuperjunction semiconductor device of claim 10, wherein drift layerincludes a first portion having the first conductivity type and a secondportion having the second conductivity type, the first and secondportions of the drift layer extend along a first direction parallel to atop surface of the semiconductor layer and are alternately arranged. 13.The superjunction semiconductor device of claim 10, further comprising alower edge region disposed below the upper charge balance region, on aside surface of the drift layer.
 14. The superjunction semiconductordevice of claim 10, further comprising: a transition region disposedbetween the active region and the termination region.
 15. Thesuperjunction semiconductor device of claim 10, further comprising: atransition region disposed between the active region and the terminationregion, the transition region at least partially surrounding the activeregion, the termination region at least partially surrounding thetransition region.
 16. The superjunction semiconductor device of claim10, further comprising: a transition region including a plurality ofpillars having the second conductivity type; and a diffusion regionconnecting the plurality of pillars.
 17. A method, comprising: forming aplurality of first active pillars and a plurality of first edge pillarsin a first semiconductor layer including an active region and atermination region; forming a second semiconductor layer on the firstsemiconductor layer; forming a plurality of second active pillars and aplurality of preliminary charge balance layers in the secondsemiconductor layer; and annealing the first and second semiconductorlayers such that the plurality of first active pillars and the pluralityof second active pillars are connected by diffusing impurities implantedinto the plurality of first active pillars and the plurality of secondactive pillars.
 18. The method of claim 17, wherein during theannealing, impurities implanted into the plurality of preliminary chargebalance layers are diffused, and adjacent layers of the plurality ofpreliminary charge balance layers are connected to form a lower chargebalance region having a tapered shape.
 19. The method of claim 17,wherein the forming the plurality of first active pillars and theplurality of first edge pillars includes respectively implantingimpurities in the active region and the termination region of the firstsemiconductor layer to form the plurality of first active pillars andthe plurality of first edge pillars.
 20. The method of claim 17, whereinduring the annealing, impurities implanted into the plurality of firstedge pillars and the plurality of preliminary charge balance layers arediffused, and the plurality of first edge pillars and the plurality ofpreliminary charge balance layers are connected.